The present invention relates to a two component developer storage product for replenishing a two component developer which includes at least toner and carrier and is used for an image forming apparatus of an electro-photographing type, and a method of filling a two component developer in a developer storage container.
In the field of an image forming technique with an electro-photographing system, it becomes possible to form a microscopic image with an image writing density of a 1200 dpi level (dpi; the number of dots per 1 inch (2.54 cm)) with progress of a digital processing technique, a semiconductor laser exposure technique, and the like. Further, the realization of such microscopic image formation makes it possible to spread the electro-photographic image to a market where a precise image with high image resolution is required.
Specific examples of the market include the print market called “on-demand printing”, and the electro-photographing system allows prints to be produced continuously in a short time without preparing a printing plate which is needed essentially in the conventional printing system. In the case where prints are produced continuously at a high rate, image formation of the two component developer type in which toner can be charged promptly by carrier is advantageous.
In image formation of the two component development type, toner is frictionally charged on the surface of carrier stored in an apparatus called a developing device, and the toner charged to a predetermined level is supplied to an image carrying member, whereby an electrostatic latent image on the image carrying member is developed. In the fictional electrification for toner conducted on the surface of carrier in the developing device, if the same carrier is used repeatedly for a long period of time, the charging performance of the carrier gradually lowers. Namely, if the same carrier is used repeatedly, a resin layer provided on the surface of the carrier wears or peels off, and the composition of toner adheres on the surface of the carrier. Accordingly, the charging performance of the carrier gradually lowers. As a result, the carrier cannot conduct required frictional electrification for toner, and in turn, a predetermined amount of toner cannot be supplied onto a photoreceptor, which results in poor development such as lowering in image density.
In order to solve this problem, adopted is a developer replenishing method called an “auto-refining development method” which feeds new carrier simultaneously with feeding of toner consumed by development and replaces the carrier in a developing device little by little, thereby maintaining the electric charge providing performance of the carrier. The “auto-refining development” is also called “trickle development” in which, for example, an additive amount is changed or carrier which is applied with a counter measure such regulation of electric resistance and the like is supplied so as to maintain the electrically charging performance of the developer in a developing device to a predetermined level (for example, refer to Patent documents 1 and 2).
For example, Patent document 1 discloses a technique that the carrier concentration of a replenishment developer is made within a specific range and a difference in electric resistance between the in-use developer in a developing device and new carrier is regulated so as to maintain the performance of the developer stably. Further, Patent document 1 discloses a technique that a plurality of replenishment developers different in electric property is prepared by use of plurality of carriers different in electric resistance value, these developers are stored separately in the same developer container, and carrier different in electric resistance value is fed selectively in accordance with the toner replenishment time so as to maintain the performance of the developer.
In this way, in the “auto-refining development”, since new carrier is also fed simultaneously with feeding of toner, in a developing device, carrier always exhibits the electric charge providing performance with a predetermined level so as to make it possible to maintain the imaging quality of produced prints stably over a long period of time.    Patent document 1: U.S. Pat. No. 3,777,778, Official report    Patent document 2: Japanese Unexamined Patent Publication No. 2004-29306, official report
As mentioned above, in the auto-refining development, although carrier is also supplied to a developing device together with toner, a replenishment two component developer stored in a developer storage container is kept in many cases in the stationary state all the time until it is supplied to a developing device. However, if toner and carrier are kept stationary for a long period of time in the state that toner is mixed with toner, shift of charge occurs on the contact portions between carrier and toner, which results in that the amount of electric charge of developer tends to become low as compared with the initial stage. Further, toner and carrier are transported in the mixed state, spent toner that toner adheres in fixture contact with the surface of carrier in receipt of the influence of vibration. Accordingly, it is considered to be desirable that toner and carrier of a replenishment two component developer are preserved separately so as to avoid contact between them until the toner and the carrier are mixed at the time of supply to a developing device.
In the case where toner and carrier are preserved separately and are mixed first when being fed to a developing device, toner and carrier are filled and preserved in respective containers separately, and a toner feeding means and a carrier feeding means are needed respectively at the time of provision to a developing device. Further, at the time of provision to a developing device, it is necessary to feed toner and carrier with a predetermined ratio, and a means to measure these accurately is also needed. Accordingly, the installation of these means to an apparatus causes increase of the number of machinery components in an image forming apparatus and makes the structure complicate, which influences cost and maintenance.
From the above reasons, in an image forming apparatus in which a developer is replenished by an auto-refining method, the developer is replenished mainly with a developer in which toner and carrier are mixed preliminary. Therefore, it is unavoidable that an amount of electric charge of a developer decreases due to contact between the toner and carrier for a long period of time and poor image is generated due to spent toner. As a result, a technique is sought to make it possible to preserve toner and carrier so as to be not likely to contact with each other in a container and to mix the toner and the carrier first with an accurate ratio when feeding them to a developing device.
An object of the present invention is to provide a two component developer storage product which forms a state that toner and carrier do not contact easily with each other in a developer storage container and can feed toner and carrier accurately with a predetermined ration when feeding them to a developing device. Specifically, an object of the present invention is to provide a two component developer storage product which avoids the contact between toner and carrier for a long period of time as far as possible by preserving toner and carrier separately in a developer storage container, whereby a electric charging ability can be prevented from lowering due to shift of electric charge between them.
Further, an object of the present invention is to provide a developer feeding method with which an opportunity to allow toner and carrier to contact with each other can be minimize, toner is not made to adhere in fixture contact with the surface of carrier even in receipt of impact during transportation of a developer storage container, and a charge providing performance of carrier can be prevented from lowering due to spent toner. Further, an object of the present invention is to provide a developer feeding method with which stores a toner layer and a carrier layer regularly in a storage container so as to feed toner and carrier with a predetermined ratio.
The above objects can be attained by the following two component developer storage product and two component developer filling method which reflects one aspect of the present invention.
A two component developer storage product to replenish a two component developer containing at least toner and carrier includes:
a cylindrical container having an opening at one end thereof;
a lid to close the opening;
a toner layer stored in the cylindrical container; and
a carrier layer stored in the cylindrical container;
wherein the toner layer and the carrier layer are stacked, and the cylindrical container has a spiral projection on an inner spherical surface thereof, and is configured such that when the cylindrical container is rotated, the toner layer and the carrier layer are conveyed by the spiral projection and toner and carrier are discharged from the opening.
A two component developer filling method for filling a two component developer containing at least toner and carrier includes in a developer storage container includes:
filling a toner layer of the toner and a carrier layer of the carrier so as to form a state of stacked layers in the developer storage container.